The Wirrn were a race of giant parasitic wasps that would like wasps we know, incubate and hatch their young in live hosts. They had spindly legs that never actually touched the ground (somehow they managed to walk by scooting on their butts?) and their grubs looked suspiciously like interns wrapped up in green bubble wrap as they scooted across the floor of the space ark. Wirrn spent most of their lives in space, but they needed to come to planets to reproduce. When humans destroyed a planet where they got many of their host animals, a band of wirrn got onto Earth’s Ark and decided great revenge would be to use the humans on board as host bodies for a new batch of wirrn. Wirrn were also able to absorb the collective knowledge of whatever host animal they laid their eggs in, so they were really looking forward to a race of super smart wirrn.

As per usual, they’re stopped before they can cause lots of trouble.

They were seen in The Ark in Space